It is well known in the art to use intervertebral implants. German document DE-A 196 22 827 describes a generic intervertebral implant. The DE-A 196 22 827 implant is constructed as a ring with an internal thread. A central feature of this implant is that there is a thread connection only with the upper, terminal part of the implant. The ring is freely movable axially, as well as rotatively with respect to the lower, terminal part of the implant. The lower, terminal part of the implant serves only as an axial stop for the ring. That is, as a supporting surface against which the ring can be twisted so that the upper, terminal part of the implant can be moved axially (nut/spindle driving mechanism). The two terminal implant parts accordingly are mounted loosely with respect to one another. The DE-A 196 22 827 implant also includes a radial, threaded borehole, through which a braceable clamping screw is passed in one of the two implant parts in order to secure the latter axially. A disadvantage of this intervertebral is that it is not secured before or during the surgery and can fall apart. For sterility reasons, there may be an appreciable time delay if an implant part were to fall to the floor of the operating room.
EP-A 1 219 266 (Ulrich) discloses a telescopable intervertebral prosthesis with a threaded ring which has straight bevel gear teeth, and that can be rotated from the radial direction over a bevel pinion. A disadvantage of the Ulrich device is that the threaded ring is not firmly connected axially with one of the sleeve parts. As a result, the implant is constructed less stably and, moreover, there is a need for a special instrument in order to bring about the traction of the implant. The bevel gear teeth, which are less “forgiving”, is a further disadvantage of this implant. In the case of a slight, axial displacement of the bevel gear teeth, the driving instrument can no longer carry out its function and the surgeon must place the instrument once again in situ.